Otimização da hidrólise enzimática de carboidratos em coprodutos do beneficiamento de arroz

Abstract

Rice (Oriza sativa L.) is one of the most important cereals in the world. Brazil plays an important role in the production of this cereal, occupying the ninth position. Its production and processing generate large volumes of coproduct, such as pre-cleaning residues, husks, broken rice, bran among others. The use of residues for ethanol production has been a relevant topic in the scientific field, as a viable alternative from a technical and economic point of view. The objective was to evaluate the technical feasibility of the coproduct from rice production as a raw material for ethanol production, based on enzymatic hydrolysis. The samples were characterized as to their content of water, ash, crude protein, ether extract, total fiber, starch and lignin. Then, alkaline pre-treatment for delignification was performed. The starch hydrolysis was performed by the action of alpha-amylase and amyloglucosidase enzymes, and cellulose by cellulase. The pre-cleaning residue showed 48.60% non-fibrous carbohydrates, 30.44% total fibers, 9.63% crude protein, 5.92% ethereal extract, 5.91% water content and 5.41% ash. And type III paddy rice presented 59.73% of non-fibrous carbohydrates, 23.39% of total fibers, 7.40% of water content, 7.18% of crude protein, 6.56% of ether extract and 3.14% of ashes. The alkaline pre-treatment reduced by 47.94 and 18.23% the lignin content for the pre-cleaning residue and for type III paddy rice, respectively. The efficiency of hydrolysis was 22.61 and 15.32% for the cellulase enzyme, and 82.18 and 87.07% for the amylolitic enzymes, both in the pre-cleaning residue and type III paddy rice, respectively. The hydrolysis with the separated enzymes showed higher yield in reducing sugar, both for the paddy rice and the residue. Therefore, the pre-cleaning residue and type III paddy rice can be considered technically feasible raw materials for ethanol production, aiming at adding value to the cereal chain.